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Calibron 12 - very difficult design from 1933 - Now with Cover

$29.95

The objective is to make a square and fit them into the large opening of the puzzle. There is only 1 solution and it is very difficult to find. We packaged the puzzle unsolved, but the solution is provided. In the frame I made an extra space to hold one of the pieces so that we could package it unsolved. Our version is made from precision cut woods with at least 4 different woods in each puzzle. Ash, Maple, Walnut, Oak, Mahogany, Birch, Cherry, Alder, and other woods may be used with each puzzle have a little unique look. The pieces are very strong at 1/4" thick and have a nice finish. I also laser engraved the relative size of each piece on the piece itself, which may be helpful to you folks who want to attack this analytically. It also makes identifying the pieces easier if you just want to use the instructions to solve it:)

Puzzle measures 9" x 7" in the base. The square opening is about 6.3" x 6.3". I have recently made and added a cover for the puzzle. It is not yet shown in the pics or video but will be included with your purchase.

One of the many things I like about this puzzle is that it does not look nearly as difficult as it actually is. People seem to get absorbed in it quite readily as you always seem to get close. It fact though, it is a difficult level 5 (of 5) puzzle.

Originally designed in 1933 by Theodore Edison, son of the famous inventor Thomas Edison, and made by his company Calibron Products of West Orange, N.J. It was offered as just pieces and you were told they made a rectangle and there was only 1 solution. Turns out the only possible solution is a square shape, as verified by Ken Irvine's computer analysis. Ken is working on a full analysis of the puzzle, with excerpts noted below. I will link that analysis here when it is available.

From Ken Irvine:

After determining that there was only 1 solution to the square (using Burr Tools program), the second goal was to determine if there were any additional rectangles that
could be made with the 12 pieces. The first step of this analysis
was to determine how many possible rectangles needed to be checked.
Since the total area of the pieces is 3136 units, the problem is to find
the set of rectangles that have an area of 3136. This is done by
factoring 3136 into its prime factors, which gives: 2 x 2 x 2 x 2 x 2 x 2 x 7 x
7. Rectangles of area 3136 can then be found by finding all
combinations of dividing the prime factors into 2 sets. This can
be further constrained by the fact that both sides need to be at least 18 units
to be able to fit the 21 x 18 piece. This results in the following
4 possible rectangles, including the original square: